Hobbing machine



Nov. 28, 1933. J. L. PERKINS El AL HOBBING MACHINE Original Filed Oct. 19, 1929 5 Sheets-Sheet l A TTORNE Y.

Nov. 28, 1933.

J. L. PERKINS ET AL HOBBING MACHINE 5 Sheets-Sheet 2 Original Filed Oct. 19, 1929 W [NI 512:5; BY 5;

7%; ATTORNEY.

NOV. 28, 1933. J L, PERKINS ET AL 1,936,730

HOBBING MACHINE Original Filed Oct. 19, 1929 5 Sheets-Sheet 3 57 w X A 99 O 1% Z5 I 100 Z4 10! 0 1' Il 10Z I m 0 INVENTORS M ATTORNEY.

NOV. 28, 1933- J. PERKINS ET AL 1,936,730

HOBBING MACHINE Original Filed Oct. 19, 1929 5 Sheets-Sheet 4 4f) Z6@ I l O m i a A TTORNE Y.

1933- J. L. PERKINS Er AL HOBBING MACHINE Original Filed Oct. 19, 1929 5 Sheets-Sheet 5 Patented Nov. 28, 1933 UNITED STATES HOBBING MACHINE Julian L. Perkins, West Springfield, and Hiram D. Croft, Springfield, Mass, assignors to Perkins Machine & Gear Company, West Springfield, Mass, a corporation of Massachusetts Application October 19, 1929, Serial No. 400,852 Renewed July 27, 1933 7 Claims.

This invention relates to improvements in machines or apparatus for cutting teeth on wormwheel blanks with hobs, which hobs are tapered and are fed endwise. The objects of the invention are, first, to produce a machine of the character described which is capable of producing a greater amount of work commensurate with the cost of the machine, and more accurate work than is possible with the ordinary hobbing rnachine; second, 'to'produce a hobbing machine which occupies much less floor space than does the machine of the ordinary type; third, to provide the machine with mechanisms which operate automatically throughout a complete cutting cycle and until the work carrier returns to starting position and said mechanisms cease to operate, something that is accomplished by no other machine; fourth, to afford means for accurately positioning and maintaining the work in proper relation to the hob; and fifth, to produce a hobbing. machine that is comparatively inexpensive to construct and economical in its operation.

The accuracy of the work done with this machine is largely due to. the automatic operation thereof, together with its ability to obtain and maintain the proper relationship between the hob and the work. It is'possible to control almost absolutely the exact number of revolutions the 0 hob makes in the machine while cutting each worm Wheel, because of the automatic operation of the mechanism, no such control being possible in machines which are largely controlled by hand.

The hobs used in our machine last longer than those used in other hobbing machines. This is because a leading or tapered-end portion thereof which begins the cut receives the most wear and is subjected to a correspondingly greater amount of grinding, while much of the full diametral portion of said hob operates to do only the lighter work or the finish cutting. Thehob, therefore, instead of being worn fairly evenly throughout its entire cutting portion is worn more throughout what may be termed the roughing part, so as to not necessitate grinding a considerable part oil of the entire hob every time that regrinding takes place.

Other objects and advantages will appear in the course of the following description.

A preferred embodiment of the invention whereby we obtain the objects and secure the advantages of the same, is illustrated in the accompanying drawings, and we will proceed to describe the invention with reference to said drawings although it is to be understood that the form,

construction, arrangement, etc., of the parts in various aspects are not material and may be modified or changed within wide limits without departure from the spirit and .scope of the invention. 1

In the drawings, in which like numbers designate like parts throughout the several views,

Fig. 1 is a top plan view of a hobbing machine which embodies a practical form of our invention.

Fig. 2 is a central, vertical longitudinal sec- 5 tional view throughthe parts and members which directly support or carry the hob and its spindle, said section being taken in a vertical plane on line 22 of Fig. 1.

Fig. 3 is a front elevational view of said machine, with certain parts broken away for clearness, and the look yoke for the Work spindle being shown by broken lines in inoperative portion.

Fig. 4 is a vertical sectional view through a, portion of the mechanism which operates the slide actuating mechanism taken on lines 44 of Fig. 1.

Fig. 5 is a right-hand end elevational view of the machine, with certain parts broken away.

Fig. 6 is a rear end elevational view of parts of the supporting and driving means for the work spindle.

Fig. 7 is a vertical sectional vew through certain work-spindle supporting and driving means on a line 7-7 of Fig. 1. v 5

Fig. 8 is a left-hand elevational view of the machine. 7

Fig. 9 is a vertical elevational view through the worm-driving mechanism, taken on line 9-9 of Fig. 1, and I I Fig. .10 is a rear elevational view of the machine. i

Parts and members are broken out in the general views in order to discloseparts and members which would otherwise be hidden.

The numeral 1 indicates generally the frameof the hobbing machine, which is mounted on a table 3 at the top of a support 5 that may be of any suitable character and will usually be constructed to rest on the floor. Surrounding the table 3 is an oil channel v7 as is customary. The frame 1 affords a guide indicated by the numeral 9 having a slide 11. The guide 9'has a horizontal slot throughthe front side with the top and bottom edges of said slotundercut to receive upper and under edges of the slide 11 which are made flaring to fit within and. engage the undercut portions of the guide so as to allow the slide to reciprocate back and forth with respect to the frame.

On the front of the frame 1 (see Figs. 2 and 3) is a support 12 provided on top with bearings 13 and 14. A horizontal spindle 15 is rotatable in said bearings and has mounted thereon secured between said bearings a cutting tool in the form of a hob 16. The support 12 is adjustably'held against the front side of the frame 1 by means of two bolts 17 and washers 18. The bolts pass through vertical slots l9l9 insaid support and are threaded in said frame.

Between a horizontal part of the frame 1 and the bottom of the support 12, which bottom inclines from the right downwardly to theleft, is a wedge 20. The wider end of the wedge 20 is at the right and there is a horizontal slot 21 in said wedge into which projects a lug 22 hired to the frame 1. A horizontal adjusting screw 23 has its head outside of the wider end of the wedge, passes through to said slot and is threaded in said lug 22.

By rotating the screw 23 to advance the same in the lug 22 the wedge 20 is caused to move to the left and raise the support 12 while upon retracting said screw, said wedge may be moved to the right and said support thereby permitted to descend. l

A lock bolt 24, on which is a lock nut 25, is tapped into and through an upstanding lug 26 on the bottom of theframe 1 andis in position to bear against the front side of the wedge 20 and, when tightened, holds said wedge against its longitudinal movement.

To adjust the support-12 up and down, the bolts 17 are loosened, also the said nut 25 and bolt' 24,

the screw 23 is'rotated to whatever extent may be necessary to bring about the required adjustment of said support by means of the wedge '20 and then all of said bolts and said nut are retightened.

The support 12 is rendered adjustable to accommodate the same to different diameters of work or worm gear blanks. A master-worm support 27 later to be described on the back side of the frame 1 is likewise rendered adjustable for the same reason'. I

A horizontal spindle 28 (see Figs. 5, 9 and 10) on which is mounted and secured a master-worm 29, is carried in the upper part of thesupport 27 referred to. On the rear side of saidsupport arebearings 30 and 31 for a horizontal shaft 32.

There are'two vertical"slots 33 in the support 27 and two bolts 34 pass through said slots which are tapped into the back side oftheframe 1; while washers 33-35 are introduced between the back side of the support 27 and the heads of said bolts. By means of the bolts and slots the support 27 and its bearings may be moved up or :down relative to the frame 1.

The bottom of the support 27 is inclined in a generally similar m'annerto that of the support 12 and a wedge 36 is introduced between the horizontal part of the framed and the lower side of the support. There is a horizontal slot 37 in the wedge 36 adjacent to the head or wider end portion thereof, and a lug 38 extends rearwardly from the frame 1 into .said slot.

An adjusting screw 39 passes through the head of the wedge 36 into the slot 37 and is tapped intoand through the lug 38. A look bolt 40 is provided for said wedge, said bolt being tapped into and through a lug 42 that rises from the bottom of the frame '1 behind in position to bind the wedge 36. v

The vertical adjustment of the support 27 is effected in substantially the same manner as is the vertical adjustment of the support 12.

A vertical key 43 (see Fig. 3) is near to the front side of the frame 1 and the back side of the support 12 to assist in maintaining said support in a horizontal position at all times, and a similar key is, for a similar purpose, is provided for the support 27. The key 44 may be held in place by a screw 45 passing through said key and tapped into the back side of the support 27, and the key 43 may be secured to the support 12 by similar means. The back of the members 12 and 27 are of course slotted to receive and slide upon their respective keys.

Mounted on and secured to the shaft 32 ou side of the bearing 31 is a pinion 46 and mounted on and secured to said shaft outside of said pinion is a gear 47.

A motor M is mounted on the table 3 behind the frame 1, and has a shaft 49 to which is secured a gear 50. The gear 50 is at the left in a position to intermesh with the gear 47, and thus cause the shaft 32 with the pinion 46 thereon to be rotated.

Projecting forwardly from the front side of the slide 11 (see Fig. 3) is a long horizontal rod 51 at the left and a shorter horizontal rod 52 at the right. These rods are adapted to carry and support a yoke 53 for the forward terminal of a work arbor or spindle 54, said yoke being pro- 1 vided with an intermediate bearing 55 for said terminal. An arm 56 projects or extends to the right from the slide 11 to afford a bearing or support for a stud 57. There is a duplicate 56" of arm 56 at the opposite or left end of the but by turning certain of the parts about or end for end, making certain other rearrangements and transpositions in some of which supports are acquired for parts in the machine as now set up, such, for example, as substitutes for the supports 12 and 27, in addition to changing the aforesaid ratchet and link mechanisms from the right-hand to the left-hand end of the slide 11, the machine may be arranged to cut left-hand worm-wheels. In short, the machine can be set up to out either rightor left-hand worm-wheels, being here setup to cut right-hand worm-wheels as previously stated.

The machine is motor driven, of course, and

electrically controlled, wherefore a control box 58 is mounted on top of the frame 1 and the mechanism of said box is connected by means of suitable wires in a cable 59 with the motor 48. On

top of the control box 58 are two push buttons 60 and 61, the former being behind the latter. I

Also mounted on the top of the frame 1 is a bearing bracket 62, and journalled in said bracket is a horizontal rock shaft 63, said shaft extending transversely of the frame 1. A hammer 64 is carried at the left-hand end of an arm 65, which is adjustably held at the right-hand terminal in a rocker 66 mounted on and secured to the shaft 63, said rocker having at the right-hand end an extension 67. The hammer 64 is supported by its L:

arm 65 and the rocker 66 over the rear push button 60. Mounted on and secured to the forward terminal of the shaft 63 is a depending trip arm 68 provided with a trip plate 69 which is rendered longitudinally adjustable on said arm by means l:

of two screws which pass through a longitudinalslot 71 in the plate 69 and are tapped into said arm.

A detent, lock. or latch 72 is pivotally connected at 72 with the brack t 62 at the right of the upright part of said bracket in which is journalled the shaft 63. The latch 72 has a part 73 capable of entering beneath the extensionfi'l of the rocker 66, when the hammer 64 is down on the pushbutton 60, to retain said hammer in said position, said latch being normally ret ined in said position by means of a spring 74 interposed between the top of the frame 1 and a tail-piece 73' which extends to the right from said latch over said frame. The latch 72 has a foot at the left-hand end underneath, which foot is indicated by the numeral '75 in Fig. 3, and the spring 74 will retain said latch with said foot on the frame 1, in which position the lock-engaging part 73 of said latch is in looking position underneath the lock extension 67. The latch 72 extends upwardly from the part 73 to form a handle to facilitate operating the latch.

A bracket 76 is fastened to the front side of the slide 11 (see Fig. 3). In the left-hand end of said bracket is a vertical slot '77; in which is a dog 78. The dog 78 is pivotally connected at 79 with the bracket 76, and is normally held with its right-hand edge against the inner edge or" the slot '77 by the spring 80.

The spring 80 has its right-hand terminal fastened to a pin 81 that extends upwardly from the bracket '16, and its left-hand terminal attached to a pin 82 that extends to the right from the dog 78 above said bracket. The trip-arm plate 69 is in the path of the upper terminal of the dog 78, which terminal inclines in the direction shown.

When the dog '78 is carried to the right with the slide 11 and encounters the trip-arm plate 69 the spring 89 will allow said dog to pass the plate. When said dog is carried with said slide to the left and encounters said plate it is buttressed against the bracket 76 and imparts to the arm 68 a swinging movement to the left, whereby the shaft 63 is rocked in a direction to swing the arm 65 upwardly and raise the hammer 64 from the button 69 provided the latch '72 be disengaged from the extension 67. Directly, however, the dog clears the plate 69 the hammer 64 drops again onto the push-button 69, and at which time the latch '72 is spring pressed into locking engagement with the extension 6'7.

Returning to the tool or hob spindle 15 andin i. e bushing 83. At 8? is a perforated disc be' tween the inner end of the bushing 83 and the chamber in the p which is received said bushing, said :1"

to-admit oil to the adjacent end of the spindle The right-hand terminal of the spindle 15 is received in an internally and externally tapered plug 88. This plug 38 received an internally tapered bushing 89 jcurnalled in the bearing i l. The bushing 89 is shouldered at the inner end to bear against the inner end of the bearing 14-,

and is held securely in place in said bearing by means of a nut 90 screwed on to the right-hand terminal of the'plug 88, which terminal extends beyond said bushing, and a washer 91 is interposed between adjacent positions of said bushing and said nut. A washer 92 is interposed between adjacent faces of said bushing and said nut while a washer 92 is interposed between the inner end of the bushing 89 and a shouldered part of the plug 88. The nut 90 when tightened together with the washer 91 draws the plug 88 firmly into engagement with the bushing 89 so that the plug 89 and the bushing 89 revolve together.

A portion 15 of the spindle 15 which is received in the tapered passage in the plug 88 is tapered to fit said passage and has therein a screw-threaded passage 93 that opens through the right-hand end of said spindle. There is also a screw-threaded passage 94 in the outer-end portion of the plug 88. A rod 95 at the inner terminal is screw-threaded as represented at 96 to engage the threads in the passage 93, and said rod has an enlarged screw-threaded part 97 at the outer terminal thereby received in and engaging the screw-threads in the passage 94 at the extreme outer end of the rod 95 is an angular head 98 for the application thereto of a wrench. Mounted on and secured to the outer terminal of the hollow plug 88 is a gear 99. When the rod 95 is screwed into the plug 88 and the shaft 15 the tapered part of said shaft is forced into tight engagement with the tapered passage in said plug. With the result that motion imparted to the gear 99 is transmitted through the plug 83 to the shaft 15 with the hob 16 thereon.

Upon loosening the clamp and withdrawing the plug as, and releasing the shaft 15 from the rod .95, said shaft 15 with its hob can be withdrawn through the bearing 13.

By the means just described the hob 16 is held firmly and securely in place, while being rotated and can be returned to place, as after grinding, or replaced, with very little difi'lculty.

The pitch diameter and form of the hob 16 are approximately the same as the pitch diameter and form of the worm which runs with the worm-wheel blank cut by said hob.

As will be observed the hob 16 has a tapering forward end and a body portion of uniform diameter. The tapering end the first to engage with the worl; and performs the rough cutting while the cylindrical body is the last to engage the work and performs the finishing operation. In th* way the tapering end is subjected to more Y and may be readily ground while the cylin- .ical body is worn to less extent and requires grinding. As will appear the rate of feed during the roughing cut may bevaried with respect to that of the finishing cut.

Adjustably secured to the right-hand of the f 'u'ne 1,

L91 an arm 192 which is provided with an outwardly extending stud 193 on which is mounted internie ate gear 194i to intermesh and dive the hob shaft gear 99. The bolt 100 passes through a longitudinal slot 195 in the arm 192 and is tapped into the contiguous end of the frame 1. A pinion 196 mounted on and secured to the right-hand terminal of the master-worm",

shaft 28 also intermeshes with the intermediate gear 19%. Upon loosening the bolt 190 and moving the 192 on said bolt the gear 104- can be adjusted properly in relation to the gear 99 and the pinion 196 and may engage any substitute by means of a bolt 199 and a washer gear and pinion that may be mounted on the lug 88 and the shaft 28, respectively, whenever a change in the diameter of the hob is made.

The shaft has one terminal journaled in a bushing 107 extending into a suitable bearing as 108 at the right-hand end of the support 27 and having a flanged part at the outer end of said bearing which is securely bolted to the bearing. The pinion 106 is mounted on a part of the shaft 28 which extends beyond the bushing 107. The other terminal of the shaft 28 is journalled in a bushing 109 located in a bearing 110 at the left-hand end of the support 27.

The shaft 28 extends beyond the outer end of the bushing 109, and mounted on and secured to this protruding part of said shaft is a gear 111. The master-worm 29 is mounted on and secured to the shaft 28 by means of a pin 112 which extends crosswise through said shaft and is received in slots in oppositely-disposed notches 113 in one terminal of said worm. A thrustbearing generally indicated by the numeral 114 is transposed between the inner ends of the bushing 109 and the bearing 110 and the adjacent end of the master-worm 29, and between the opposite end of said worm and a washer 113 which is located against the inner end of the bushing 107. Suitable lubricating means are provided for the bushings 10? and 109.

As will be seen from Figs. master-worm shaft 28 is driven from the motor M by gears 50, 47, 46 and 111, while the hob shaft 15 is driven from the master-worm shaft 23 by means of the gears 106, 104 and 93.

The construction of the work or worm gear supporting spindle or arbor will now be described with particular reference to Figs. 6 and 7. The spindle 54. is slidable and rotatable in bearings and 1 1 of the slide 11 and is adapted to carry on its forward end a piece or work such as a worm-gear blank W. Theouter end of the spindle is adapted for rotation in the bearing 55 of the yoke 53 as shown in Fig. 3. A worm gear 123 is rotatable on a rearwardly extending bearing 124 of the slide 11 and carries on its outer side a hollow hub 123', the outer open side of which is capped by a plate 125 secured thereto by screws 126.

The worm-gear 123 is held against axial movement by means of a collar 127 screw threaded on the end of bearing 124 and suitable oil channels and grooves as shown are provided for lubricating the parts.

An apertured disc 129 for r ceiving an end of spindle 54 and located within the hollow hub is spring pressed inwardly from the plate 125 by means of springs 130 and is provided with oppositely dispose tongues 131 which slide in suitable slots 132 in opposite walls of the hub 124 of the gear. A set screw 133 in one of said tongues is arranged to clamp the end of the spindle to the disc. The disc rotates with the gear and thereby rotates the spindle 54 and gear blank carried on the forward end thereof.

By loosening the set screw 133 the spindle may be withdrawn through the bearings to facilitate the substitution of an unfinished gear blank on its outer end for a finished blank.

As will be seen the worm-gear 123 is in mesh with and driven by means of the worm 29 therebelow so as to rotate the work spindle and the blank W pressed thereon in proper timed relation with respect to the cutting or forming tool or element 16. It will be noted that since the spindle is slidable with the disc 129 to which it 5 and 9 the may be fixed by means of the set screw 133 that it is possible for the spindle to adjust itself so that work carried thereby may be positioned accurately with respect to the tool. For this purpose the work may be thrust against the slide 11 by the forming action of the tool. To allow this the disc 129 may be urged against the springs by the so-called thrusting action of the tool.

By rotating the work spindle by means of the worm and worm-gear and by rotating the hob shaft therefrom by means of the gears described it is possible to employ hobs of various forms to produce various forms of worm gears. At all times the work spindle and hob shaft may be rotated at predetermined relative speeds to obtain the desired results.

Means for feeding the slide 11 back and forth so as to cause the gear blank and rotating hob to be moved relative to one and another for the cutting ortooth forming operation will now be described with particular reference to Figs. 1, 3, 4, 5, 9 and 10.

The supporting stud 57 at the rear or right of the slide in Fig. 3 has fixed thereon a bracket 135. A ratchet wheel 136 and cams 137 and 161 associated therewith are rotatable on the stud 57. The cam 137 is arranged so that its periphery rides upon a roll 140 at the end of a. member 141 adjustably fixed on the frame 11. The slide is forced to the left so that cam 137 bears against the roll 140 by means of a weight 142 connected to the slide by a cable 142 which passes over suitable gnide sheaves 144. As the cam is rotating counter clockwise its increasing diameter moves the slide to the right to feed the blank W against 110 the hob. This movement is against the action of the weight so that according to the shape of the cams the weight is allowed to return the slide to the left at the end of the feeding movement.

A shaft oscillatable in the member 135 has 115 fixed to its opposite ends a slotted lever 151 and a. depending arm 152 to which arm is pivoted a spring pressed pawl 153 for engaging the teeth of the ratchet 136.

A connecting rod 154 is pivoted at 155 to the 120 plate 125 of gear 123 and carries on its upper end a link 156 which is pivotally and adjustably mounted in the slotted lever 151. As the gear 123 rotates the lever 151 is rocked to and fro to actuate the pawl 153 and thereby feed the ratchet 125 and rotate the earns 50 that the slide is moved in its feeding movements to the right in Fig. 3. A second pawl 160 pivoted on the member 135 is spring pressed towards the ratchet wheel for engaging the teeth thereof and functions as a check to prevent the ratchet wheel from moving rearwardly.

The cam 161 fixed to the face of ratchet wheel 136 has a peripheral nose 162 which in the rotation thereof engages the underside of a lever 163 pivoted to bracket 135 and is adapted to elevate the said lever. This lever is arranged to engage the underside of a pin 164 extending forwardly from the ratchet 153 and on raising will raise the pawl from operable engagement with 149 the teeth of the ratchet.

A ring fixed to the rear side of the ratchet wheel 136 has a diverging tapering peripheral face as shown in Fig. 4. A floating annulus 171 about the ring has an internal surface to fit that 145 of the ring and is urged outwardly from the ratchet wheel by means of springs 172 and balls as shown. A pin 173 projecting from the annulus 171 is arranged to abut the bracket 135 as shown in Fig. 10 so as to be held against ro- 7,5

tation. As the annulus is urged into frictional engagement with the ring by means ofsprings the ratchet and camsare frictionally held against rotation to the extent that they are prevented from over traveling or from rotating in a reverse direction.

The slide feeding mechanism is preferably so constructed and arranged that as the slide at first moves to feed the work against thehob the rate of travel is relatively less than at the completion of the feeding movement at which time the hob is in reality finishing the work as distinguished from its first rough cutting. This is accomplished by suitably shaping the'cams 1S? and 161, the lat-- ter of which is arranged to elevate t.-e lever 163 and pawl 153 at the proper time so that more or less teeth of the ratchet wheel are engaged the pawl which will vary the rate of travel of the cam.

The yoke 53 is slidable back and forth on the rods 51 and 52 and the left hand end is provided with a clamping screw 180 as shown. A stop stud 181 projecting forwardly from the slide is disposed in the path of a lug 182 of the yoke so as to act as a stop for the yoke as it is pulled forwardly of the rods and swung to the upper dotted line position shown in Fig. 3. As the yoke is moved forwardly of the rods the forward end of the work spindle slips through the bearing 55 thereof so that after being swung upwardly the spindle may be moved forwardly and removed from the machine.

In operation work such as a gear blank W is placed on the work spindle which is inserted in and operatively'connected to the worm gear 123. The yoke is then swung downwardly and moved rearwardly on its supporting rods so as to receive and support the forward end of the work spindle. It is then looked in place by means of the screw 180. At this time the slide 11 is in the left hand position or rest position shown in Fig. 3, and the latch '72 is swung to the right to release the dog lever and weight 64. The starting button 61 is pressed so that the motor M is operated. The master-worm 29 and shaft 28 are rotated for driving the work spindle while the hob and its shaft 15 is rotated for the blank cutting operation. The ratchet wheel 136 is urged forwardly so so as to rotate the cams 137 and 161 and in that way feed the slide to the right against the action of the weight so that the work is brought into cutting engagement with the hob. In the feeding movement the rotating work is fed against the rotating tapering hob which according to its particular form cuts the desired teeth in the periphery of the blank.

By arranging the feeding mechanism the parts may be adapted to vary the feeding movement during a cycle of operation so as to adapt the machine to various types or kinds of work. That is the feeding mechanism is preferably arranged so that the work approaches and engages the tapered portion of the hob at a comparatively slow rate of speed at which time the worm is performing a rough cutting operation. Later when the teeth are fairly well shaped and the full diameter of the hob is in engagement with the blank the rate of travel of the slide is greater. At this time the out being made in relatively less than formerly and is in effect a finishing cut so that with an increased rate of travel the hob is not called upon to perform an excessive amount of work.

At the completion of the feeding movement of the slide and at which time the work is machined or cut to the extent desired, the dog '78 on the slide passes by the depending plate -69. At thistime the large diameter of the cam 13'? passes by the roll 140 so that the carriage ismoved by the weight to its rear or left-hand'position. In this position the work spindle may be removed by swinging the yoke upwardly.

As the slide is traveling to the left the dog '78 strikes against the plate 69 so as to swing and elevate the hammer 64- and as it passes by the end of the plate the hammer drops so-as to strike upon buttton so and in that way cuts off current to the motor. The spring 74 beneath the latch i2 causes it to swing into position to lock-th lever 66 in button depressing-position.

It will be readily obvious that various combinations of gears may be employed to connect the motor to the master worm shaft and work spindle and to connect the master-worm shaft'to the hob shaft so that various relative speeds and relative directions of rotation of the Work spindle and hob may be attained. By selecting suitable gears the machine maybe adapted to produce an unlimited number of cut gear blanks of different forms or types. 7

Also it will be noted that by driving the work spindle and hob shaft from what may be called a common driving element that extreme'accuracy in relative speeds may be attained to facilitate the production of correspondingly accurate work.

As one special feature it will be observed that by employing a hob of tapering diameter that it is possible to follow a rough cutting portion of the cycle of operation by a finishing out so that relative speeds may be employed which are best adapted for the out being made, all to the end that efficiency in operation, accuracy of product and economy inits'cost may-result.

We are aware that various changes and modifications may be made in'theform of the apparatus without departing from the spirit and scope ofthe invention and therefore we prefer to be limited, if at all, by the appended claims and not by the foregoing description which is for purposes of disclosing the present preferred form of the invention.

What we claim is:

1. In an apparatus of the class described, a support having spaced bearings, a drive shaft journalled in said bearings, a master-worm on said shaft between said bearings, a tool shaft rotatable in said support, a slide reciprocable on said support having a work shaft rotatable therein arranged so that the axis of said shaft moves between said spaced bearings, a gear on said work shaft in mesh with said master worm, connections between said drive and tool shafts, a cam rotatable in said slide bearing on a part of said support for reciprocating said slide, a ratchet wheel associated with said cam, a pawl engaging said ratchet and connections between said work shaft and pawl whereby the latter is actuated by the former.

2. In an apparatus of the class described, a support having spaced bearings, a drive shaft journalled in said bearings, a master-worm on said shaft between said bearings, a tool shaft rotatable in said support, a slide reciprocable on said support having a work shaft rotatable therein arranged so that the axis of said shaft moves between said spaced bearings, a gear on said work shaft in mesh with said master-worm, connections between said drive and tool shafts, a cam rotatable in said slide bearing on a part of said support for reciprocating said slide, a ratchet wheel associated with said cam, a pawl engaging said ratchet and connections between said work shaft and pawl whereby the latter is actuated by theformer, means for moving said pawl from engagement with said ratchet including a cam associated with said first named cam.

3. In an apparatus of the class described, a support having spaced bearings, a drive shaft journalled in said bearings, a master-worm on said shaft between said bearings, a tool shaft rotatable. in said support, a slide reciprocable on said support having a work shaft rotatable therein arranged so that the axis of said shaft moves between said spaced bearings, a gear on said work shaft in mesh with said master-worm, connections between said drive and tool shafts, a cam rotatable in said slide bearing on a part of said support for reciprocating said slide, a ratchet wheel associated with said cam, a pawl engaging said ratchet-and connections between said work shaft and pawl whereby the latter is actuated by the former, means for moving said pawl from engagement with said ratchet including a cam associated with said first-named cam and means associated with said cams to frictionally hold the same against rotation.

4. In an apparatus of the class described comprising in combination, a support having a master worm and a tool shaft rotatable therein, a slide reciprocable on said support having a work shaft rotatable therein with a gear thereon in mesh with said worm, a cam journalled on a stud of said slide engaging a part of said support for moving said slide in one direction, a ratchet associated with said cam, an arm on said stud carrying a pawl forurging said ratchet in one direction and connections between said work shaft and arm whereby said cam is urged in one direction from said work shaft.

5. In an apparatus of the class described comprising in combination, a support having a master worm and a tool shaft rotatable therein, a

slide reciprocable on said support having awork shaft rotatable therein with a gear thereon :in mesh with said worm, a cam journalled on a stud of said slide engaging a part of said support for moving said slide in one direction, a ratchet associated withsaid cam, an arm on said stud carrying a pawl for urging said ratchet in one direction and connections between said work shaft and arm whereby said cam is urged in one direction from said work shaft, a lever on said arm engageable with a part of said pawl for moving the pawl away from said ratchet and means associated with said cam for actuating said lever.

6. In an apparatus of the class described comprisingin combination, a support having a master worm and atool shaft rotatable therein, a slide reciprocable on said support having a work shaft rotatable therein with a, gear thereon in mesh with said worm, a cam journalled on a stud of said slide engaging a part of said support for moving said slide in one direction, and mechanism associated with saidcam and work shaft arranged whereby the cam is actuated by the work shaft.

'7. In an apparatus of the class described comprising in combination, a support having a master worm and a tool shaft rotatable therein, a

slide reciprocable on said support having a work shaft rotatable therein with a gear thereon in mesh with said worm, a cam journalled on a stud of said slide engaging a part of said support for moving said slide in one direction, mechanism associated with said cam and work shaft art ranged whereby the cam is actuated by the work shaft, the said cam and part arranged to move said slide a certain distance in said one direction and permit the slide tov be moved in an opposite direction and means to move said slide in said opposite direction. 

